The present invention relates generally to textile fabrics and fabric producing methods and, more particularly, to warp knitted textile fabrics of the type commonly referred to as spacer or double plush Raschel fabrics produced on a double needle bar Raschel warp knitting machine, to products produced from such fabrics, and to warp knitting methods for producing such fabrics.
Double needle bar Raschel warp knitting machines are basically equipped with two independently operated needle bars fed with multiple warps of yarn from a plurality of respective warp beams through a corresponding plurality of yarn guide bars. One common application of such knitting machines is to produce a so-called spacer or double plush pile fabric having two separate spaced-apart ground fabric structures integrated by one or more traversing yarns extending between and interknitted with the two ground structures. Spacer fabrics of this type are typically produced from five or more sets of warp yarns separately wound on individual warp beams and fed to the two needle bars through a corresponding set of yarn guide bars, normally with at least two sets of warp yarns fed through two corresponding guide bars exclusively to one of the needle bars to fabricate one ground structure, at least two other sets of warp yarns fed through other corresponding guide bars exclusively to the other needle bar to fabricate the other ground structure, and the remaining sets of warp yarns fed through one or more of the remaining available guide bars alternately to the two needle bars to extend between and interknit with the two ground structures and thereby to integrate and maintain the ground structures in spaced-apart essentially parallel relation.
Traditionally, double needle bar Raschel spacer fabrics of this type have been utilized as a means of producing two warp-knitted pile fabrics at once, the two ground structures of the spacer fabric being separated subsequent to knitting by a cutting operation wherein a cutting blade severs the traversing yarns intermediate the two ground structures leaving each ground structure with a plush pile surface produced by the outwardly extending portions of the severed yarns. More recently, however, attention has been directed to applications and uses of double needle bar Raschel spacer fabrics which are left intact as knitted without undergoing any cutting operation. Because the traversing pile yarns in such fabrics lend a three-dimensional quality to the fabrics and provide some degree of compressibility and resiliency across the thickness of the fabric, it has been proposed that such fabrics could be utilized as an acceptable substitute for conventional fabric-laminated foam materials such as neoprene and polyurethane.
Such applications of spacer fabrics offer several potentially significant advantages. First, since many textile fiber and filamentary materials are recyclable, the use of spacer fabrics as a cushioning material overcomes the inability of foams to be recycled and the attendant problems associated with disposal of such materials. Also, spacer fabrics offer substantially enhanced air and moisture permeability over foams, which makes such fabrics more desirable than foam materials for use in shoes, foundation garments, other garments, medical supports and wraps, athletic wraps and braces, etc., worn on the body. Additionally, spacer fabrics would eliminate the common necessity of laminating a fabric material to one or both surfaces of a foam material and thereby have the potential for improved production efficiency and lower cost in comparison to fabric-backed foam materials.
On the other hand, spacer fabrics present some difficulty in replicating certain of the physical characteristics of foam materials such as compressibility, resiliency, modulus and power. While spacer fabrics have a certain degree of inherent compressibility and resiliency, it has proven difficult in practice to engineer and design for any given conventional foam material a spacer fabric which is comparable both in physical characteristics of compressibility, resiliency, stretchability, modulus and power and in dimensional thickness as well, while also achieving a comparable hand and feel. Further, spacer fabrics characteristically have the tendency for the two opposing ground fabric structures to shift and move in parallel with respect to one another when opposing forces are applied to the opposite fabric surfaces in a direction parallel to the fabric's lengthwise or widthwise dimension, commonly referred to in the industry as shear.